1 10 E. A. Andrews — Anatomy of the Sjnder Crab. 



Hepju'iiting tlie lower part of" tlie cardiac and j>yloric regions, on the 

 sides of wliicli two processes {ip") run forward to join the posterior 

 cardiac ossicle, or rather the ossicles forming its rim. The pi'ineipal 

 chitinous pieces vi^iljle on the exterior of the pylorus are thus twenty- 

 seven in number, three median and twenty-four in pairs. 



The inner walls of the lateral pouches (o) are continued into the 

 cavity of the pylorus as a stout median ridge, filling most of the nar- 

 row space between the postero-lateral pyloric plates {pp) and giving 

 rise at its posterior edge to a transverse, lanceolate, valvular process 

 which extends upward into the cavity and with the posterior ))air of 

 superior valves nearly closes the more open upper part of the pylorus. 

 The two pairs of superior valves are lanielliform processes arising 

 from the upper walls of the pylorus, fringed with setre, and forming, 

 when brought in contact, a straining apparatus. The anterior pair 

 are prolonged backward from the upper wall of the middle pouch 

 and have free triangular terminations. The posterior pair are curved 

 ridges arising from the anterior edge of the thii'd pouch. There is 

 also a setose ridge on either side of the cavity of the pylorus, imme 

 diately above the postero-lateral plate, and a small setose papilla in 

 advance of the origin of each antero-superior valve. 



The chief muscles by which the chitinous skeleton is set in motion 

 so as to bring the toothed processes in contact with one another, and 

 which also aid in holding the stomach in place, are the anterior and 

 the posterior gastric muscles {ag.pg^ figs. 1, 19). The former pair 

 extend from the cardiac and pterocardiac ossicles forward to a pair 

 of laraelliform processes, arising from the sternal wall a little above 

 the insertion of the optic peduncles. The pair of postei'ior gastric 

 muscles pass back from the prepyloric and pyloric ossicles to the 

 carapace, where they are attached to small transverse ridges on each 

 side of the median line. There are also two other pairs of muscles on 

 the dorsal face of the stomach, the cardio-pyloric {cp^ fig. 1), extend- 

 ing from the pterocardiac ossicles to the prtepyloric ossicle, and the 

 supero-pyloric muscles {sp^ fig. 1, 19), extending directly upward 

 from the triangular mesopyloric ossicles to the carapace, where they 

 are attached to a pair of disk-shaped processes. 



On each lateral face of the stomach there are three extrinsic mus- 

 cles: a stout, long muscle (»*, tig. 19) extending from the interior of 

 the two calcified areas on the side of the cardiac portion of the 

 stomach forward to the roof of the efferent canal in advance of the 

 mandi))le {in. fig. 20), and attache<l to a ridge on the surface ; and 

 two long, slender muscles (wi', ?//', fig. 19), extending from the lower, 



